In known crane controllers a control or regulation usually is employed, in which the desired position or velocity of the load serves as setpoint. For example, the crane operator specifies a desired velocity of the load via a hand lever, which then serves as input variable for the crane controller.
The inventors of the present disclosure have recognized that such actuation of the hoisting gear can be disadvantageous in certain constellations.
Therefore, it is the object of the present disclosure to provide an improved crane controller.
In accordance with the present disclosure, this object is solved by a crane controller for a crane which includes a hoisting gear for lifting a load hanging on a cable. According to the present disclosure, the crane controller has a cable force mode in which the crane controller actuates the hoisting gear such that a setpoint of the cable force is obtained. Such actuation of the hoisting gear on the basis of the desired force which acts in the cable can have advantages for certain hoisting situations as compared to a crane controller which operates with reference to a target position or target velocity of the load. In particular, the generation of a slack cable when setting down the load can be prevented by the cable force mode of the crane controller according to the present disclosure. Advantageously, the actuation is effected automatically.
In one example, the velocity and/or position of the winch is actuated. In particular, the velocity and/or position of the winch can be actuated by taking account of the elasticity of the system such that the setpoint of the cable force is obtained.
Advantageously, in the cable force mode the cable force can be maintained at a constant setpoint. Advantageously, in the cable force mode the crane controller actuates the hoisting gear such that the cable force is automatically adjusted to a specified setpoint.
There can be provided a cable force determination unit which determines an actual value of the cable force. Advantageously, the actuation then is effected on the basis of a comparison of the actual value and the setpoint value of the cable force.
According to the present disclosure, in the cable force mode the cable force can be controlled by feedback of at least one measured value. Advantageously, the cable force determination unit determines the actual value of the cable force on the basis of a measurement signal of a cable force sensor.
According to the present disclosure, the cable force sensor can be arranged at the hoisting gear, in particular at a mount of the hoisting winch and/or a mount of a cable pulley. For example, the cable force sensor can be arranged in a tab which fixes the hoisting winch on a hoisting winch base, or which holds a cable pulley through which the hoisting cable is guided.
Furthermore, the cable force determination unit can determine the actual value of the cable force via a filtration of measured values or a model-based estimation. In particular, an observer can be provided, which determines the cable force on the basis of measured values as well as a physical model of the dynamics of the cable.
Furthermore, the crane controller according to the present disclosure can include a setpoint determination unit which determines the setpoint of the cable force with reference to measured values and/or control signals and/or inputs of a user.
For example, the setpoint determination unit can determine the static force acting on the cable during a lift. In particular, the static force acting on the cable can be determined during a lifting operation preceding the cable force mode. The static force in particular corresponds to the weight of the lifted load. The dynamic part of the forces acting in the cable can be removed for example by filtration.
Furthermore, the cable length can be included in the setpoint determination unit in accordance with the present disclosure. Especially during lifts with great cable length, the load acting at the cable suspension point also depends on the length of the unwound cable and its weight, respectively. Advantageously, the setpoint determination unit therefore takes account of the weight of the unwound cable.
In particular, the weight of the lifted load can be determined in that with a free-hanging load the weight of the unwound cable is deducted from a static part of a measured force. Advantageously, the setpoint determination unit then takes account of the weight of the lifted load thus determined and the weight of the cable currently unwound in the cable force mode.
A setpoint determination unit which takes account of the cable length in particular is advantageous when the cable force is measured via a sensor which is arranged not on the load hook, but for example on the hoisting gear.
Furthermore, a crane controller according to the present disclosure can comprise an input element via which the crane operator can vary the setpoint of the cable force. The crane operator thereby can set which tension is to be maintained in the cable during the cable force mode.
Advantageously, a corresponding factor can be entered, which determines the ratio between the setpoint of the cable force and the static force during a lift. For example, the crane operator thus can specify that during the cable force mode at least a part of the cable force should be in a certain ratio to the weight force of the load previously acting on the cable.
Advantageously, the setpoint of the cable force is determined such that it always lies above the weight force generated by the unwound load cable. It thereby is ensured that no slack cable can be obtained in the cable force mode. As already described above, the cable length advantageously is taken into account for this purpose and the weight of the unwound cable is determined. In particular, the setpoint of the cable force can consist of the sum of the weight force generated by the unwound load cable and a force which is in a particular ratio to the weight force of the load previously acting on the cable.
In the cable force mode, the crane controller according to the present disclosure can comprise a pilot control part, which takes account of the dynamics of the cable, and a feedback part, via which the cable force determined by the cable force determination unit is fed back. For example, the pilot control part can be based on the inversion of a model describing the vibration dynamics of the cable. Advantageously, the same takes account of the weight of the unwound cable. The actuation then is stabilized via the feedback part.
Furthermore, the crane controller according to the present disclosure can include a state detection, wherein the crane controller automatically switches into and/or out of the cable force mode with reference to the state detection. Advantageously, the state detection can detect setting down and/or picking up of the load. The crane controller thereby can automatically switch into or out of the cable force mode, when it recognizes such setting down or picking up of the load.
Alternatively, switching in one or in both directions also can be effected manually by the crane operator.
Advantageously, the state recognition each can indicate the current state.
Advantageously, the state detection monitors the cable force, in order to detect the state of the crane and in particular to detect setting down and/or picking up of the load. Advantageously, setting down of the load is recognized when a negative load change exists and/or when the derivative of the cable force lies below a certain threshold value, whereas the crane operator specifies lowering of the load via an input device, such as a joystick or a touch screen. Conversely, picking up of the load can be recognized when a positive load change exists and/or when the derivative of the cable force lies above a certain threshold value, whereas the crane operator specifies lifting of the load via an input device.
The crane controller according to the present disclosure furthermore can comprising a lifting mode, in which the hoisting gear is actuated on the basis of a setpoint of the load state or cable state, such as the load position and/or the load velocity and/or on the basis of a setpoint of the cable position and/or cable velocity. There can be provided a controller which in the lifting mode feeds back an actual value of the load position and/or load velocity and/or cable position and/or cable velocity.
Advantageously, the crane controller switches from the lifting mode into the cable force mode, when it detects setting down of the load.
Furthermore, the crane controller or the crane operator can switch from the cable force mode into the lifting mode, when the crane controller detects and possibly indicates picking up of the load.
The crane controller according to the present disclosure particularly can be used during lifts in which either the cable suspension point or the load deposition point moves, as is the case due to the heave for example in cranes arranged on a ship or with loads to be deposited on a ship.
Due to the cable force mode according to the present disclosure, the occurrence of a slack cable can be prevented despite a movement of the cable suspension point or the load deposition point, since a constant tension is maintained in the cable via the cable force mode. The partly enormous loads acting on the cable and on the crane, which can be generated in slack-cable situations, thereby are avoided.
The crane controller according to the present disclosure can include an active heave compensation which by actuating the hoisting gear at least partly compensates the movement of the cable suspension point and/or a load deposition point due to the heave. An even further improved actuation of the crane thereby can be achieved during heave.
Advantageously, the active heave compensation is effected on the basis of a prediction which predicts the future movement of the cable suspension point or load deposition point due to the heave and at least partly compensates the same by a corresponding actuation of the hoisting gear.
The active heave compensation can be employed in the lifting mode and/or in the cable force mode of the crane controller according to the present disclosure.
The present disclosure furthermore comprises a crane with a crane controller as it has been described above.
In particular, the crane according to the present disclosure can be a deck crane. A deck crane is a crane which is arranged on a pontoon. In such cranes, the cable suspension point therefore can move due to the heave.
Alternatively, the crane according to the present disclosure for example also can be a harbor crane or offshore crane or cable excavator, in particular a mobile harbor crane. A harbor crane is used to load loads onto a ship or unload the same from a ship. A crane according to the present disclosure therefore can also be installed on a drilling platform. In such cranes which are used for loading or unloading a ship, the load deposition point can move due to the heave.
The present disclosure furthermore comprises the use of a crane controller according to the present disclosure in lifting situations in which the cable suspension point and/or the load deposition point moves due to external influences such as for example due to the heave. External influences, however, also may be wind loads which move the cable suspension point.
Here, the cable force mode according to the present disclosure can prevent that a slack cable is obtained due to this external movement. The cable suspension point in particular can be the crane tip, from which the hoisting cable is guided to the load. When the same is moved for example due to the heave, this movement is transmitted to the cable and hence to the load. The load deposition point for example can be the loading area of a pontoon, in particular of a ship. When the same is moving with the load set down, either a slack cable can be obtained or the load can be lifted.
The present disclosure furthermore comprises the use of a crane controller according to the present disclosure with the load set down. In particular, the cable force mode according to the present disclosure automatically ensures that a desired setpoint of the cable force is maintained. Advantageously, this is effected by a control of the cable force according to the present disclosure.
The present disclosure furthermore comprises a method for actuating a crane which includes a hoisting gear for lifting a load hanging on a cable. According to the present disclosure, the hoisting gear is actuated on the basis of a setpoint of the cable force. This also provides the advantages which have already been set forth above in detail with regard to the crane controller and its use.
Advantageously, the method is effected such as has already been described above in detail with regard to the crane controller according to the present disclosure and its use.
In particular, the method according to the present disclosure can be carried out with a crane controller as it has been described above.
Advantageously, the crane controller according to the present disclosure automatically switches into the cable force mode upon detection of a depositing operation. Advantageously, a ramp-shaped transition is effected from the force currently measured on detection of the depositing operation to the actual target force, in order to avoid setpoint jumps in the reference variable.
Furthermore, for lifting the load the target force initially can be raised to such an extent that the load is lifted. Furthermore advantageously, switching from the target force mode to the lifting mode is carried out with free-hanging load.
Advantageously, the crane operator can manually switch from the cable force mode into a lifting mode. Alternatively, this is effected automatically by the crane controller.
Furthermore advantageously, the input device via which the crane operator specifies the movement of the load in the lifting mode also is deactivated automatically during the cable force mode.
The present disclosure furthermore comprises software with code for carrying out a method as it has been described above. The software can be stored on a machine-readable data storage medium. Advantageously, a crane controller according to the present disclosure can be implemented by the software according to the present disclosure, when it is installed on a crane controller.
The crane controller according to the present disclosure and in particular the cable force mode advantageously is realized by an electronic control unit. In particular, a control computer can be provided, which is connected with input elements and/or sensors and generates actuation signals for actuating the hoisting gear. The control computer furthermore can be connected with a display device, which visually displays information on the state of the crane controller to the crane operator. Advantageously, it is indicated according to the present disclosure whether the crane controller is in the cable force mode and/or in the lifting mode. Furthermore, the setpoint can be visualized according to the present disclosure. Advantageously, the control computer is connected with an input element via which the desired cable force can be set. Furthermore advantageously, the control computer is connected with a cable force sensor.
The present disclosure will now be explained in detail with reference to an exemplary embodiment and drawings.